GYP->GN of Skia's arm64 rules in skia_library_opts.gyp
GYP->GN of Skia's arm64 rules in skia_library_opts.gyp

BUG=568883

Review URL: https://codereview.chromium.org/1515103002

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#365543}

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